1. Field of the Invention
The present invention relates to a digital TV, and more particularly to a method and apparatus for processing received video data of different video formats.
2. Discussion of the Related Art
A digital TV may receive an NTSC signal or an VGA signal. Accordingly, if one were to examine the number of signal lines necessary for interfacing an NTSC signal with a digital TV receiver, only one pin is required for the analog NTSC signal. Because an analog signal includes the luminance signal Y, the carrier color signal C, and the horizontal/vertical synchronizing signals, one pin can interface an analog NTSC signal. However, more than one is necessary if the NTSC signal is digitized before interfacing the signal with the digital TV.
The VGA signal also requires more than one pin. Specifically, five pins are necessary for interfacing the VGA signal which includes Red (R), Green (G), Blue (B), and vertical/horizontal synchronizing signals. Therefore, if the NTSC and the VGA signals are simultaneously processed, a great number of signal lines are necessary for interfacing the signals, thereby requiring a complicated hardware.
Moreover, additional memory is required during the VGA signal interfacing if the difference between the locations of synchronizing signal intervals and effective data is ignored. For example, a horizontal synchronizing (Hsync) signal is shown in FIG. 1 (b) with respect to the clock shown in (a). However, because the signals Y and C are underscanned, the Y and C signals are generated after the Hsync signal as shown in (c) and (d), by a period of nvin_h. Referring to FIG. 2(b), a vertical synchronizing (Vsync) signal is generated with respect to the Hsync signal shown in (a) and the actual video data is also generated after the Vsync by a period of nvin_v shown in (c). As a result, the VGA synchronizing signal and the VGA video signal have different starting points, causing a storage of a portion without an actual video image. The different starting points causes a waste of memory space.